Currently, the major focus is on mechanisms of bone loss in primary and secondary hyperparathyroidism. Specifically, we have observed that in primary hyperparathyroidism interleukin-6 levels are elevated and correlate strongly with markers of bone turnover. We, therefore, hypothesize that IL-6 maybe a proximate mediator, or at least marker, for bone loss in primary hyperparathyroidism. We are undertaking a prospective study in which we will follow patients with primary hyperparathyroidism over time, correlating rates of bone loss as measured by bone densitometry, with circulating levels of IL-6. We have identified a subgroup of patients with osteoporosis who have secondary hyperparathyroidism due to intestinal calcium malabsorption. These patients have evidence of preferential osteopenia at the hip. The pathophysiology of this disorder is being explored.